1. Chapter 6
The Muscular System

2. The essential function of a muscle is to shorten or contract
As a result of this ability, muscles are responsible for almost all body movement and can be viewed as the “machines of the body”

3. Overview of Muscle Tissues

4. Muscle Types - Three
Skeletal
Cardiac
Smooth

5. The 3 Types of Muscle Tissue differ in:
Cell structure
Body location
How they are stimulated to contract

6. The three types of muscle tissue are similar because:
All muscle cells are elongated – called muscle fibers
The ability of muscle to shorten or contract depends on 2 types of myofilaments (part of the cytoskeleton)

7. Skeletal Muscle
Fibers are packaged into skeletal muscles that attach to the skeleton
Cigar-shaped
Multinucleate (many nuclei)
Largest of the muscle fibers

8. Striated muscle (appear striped)
Voluntary muscle (conscious control)
Form smoother contours of the body

9. Key words to think of for skeletal muscle:
Skeletal, striated, voluntary

10. Skeletal muscles are very fragile, but they are capable of exerting tremendous power.
They are able to do this because:
thousands of fibers are bundled together with connective tissue – these bundles are then bundled together

11. Tendons
Attach muscle to bone

12. Figure 09.02

13. Functions of the tendons
Anchor muscles
Provide durability and conserve space
Crossover bony projections

14. Smooth Muscle No striations Involuntary
Found in the walls of hollow digestive organs
Propels substances along a definite path

15. Spindle shaped
Single nucleus
Arranged in sheets or layers
Muscle contraction is slow and sustained

16. Key words:
Visceral, non-striated, involuntary

17. Cardiac Muscle
Found only the heart
Striated and involuntary

18. Key Words:
Cardiac
Striated
involuntary

19. Muscle Functions
Muscles play four important roles in the body.

20. 1. Produce movement
Moves the body

21. 2. Maintain posture
Allow you to remain in an erect or seated posture despite gravity

22. 3. Stabilize Joints
Muscle tendons are extremely important in reinforcing and stabilizing joints

23. 4. Generating Heat Heat is a by product of muscle activity
ATP used as power – ¾ escapes as heat

24. Microscopic Anatomy of Skeletal Muscles
Skeletal muscle contains both actin and mysosin filaments
The overlapping pattern of thick and thin filaments is responsible for the light and dark bands seen in skeletal striated muscle

25. The thick filaments are made up of a protein called myosin
The thin filaments are made of a protein called actin.
Sarcomere: contractile unit

26. Skeletal Muscle Activity

27. The 2 special functional properties of muscles:
Irritability – ability to receive and respond to a stimuli
Contractility – ability to shorten with adequate stimuli
Skeletal muscles must be stimulated by nerve impulses to contract.

28. Motor Unit
One neuron (nerve cell) and all the skeletal muscles it stimulates

29. Figure 09.09

30. How a muscle contracts
A nerve impulse reaches the end of the nerve a neurotransmitter is released.
The neurotransmitter that stimulates skeletal muscle is acetylcholine (Ach)
When enough acetylcholine is released, sodium ions (Na+) will rush into the muscle.
This rush of ions creates an electrical current known as the action potential.
The action potential travels over the entire muscle causing it to contract.

31. The events that return a muscle to its resting state:
Diffusion of K+ (potassium) out of the cell
Activation of the Na+/K+ pump

33. The Sliding Filament Theory
Muscle fibers contract when the sarcomere shortens.
The sarcomere shortens when the actin fibers slide past the myosin filaments
Myosin moves the actin.

34. The sliding filament theory refers to the movement of actin in relation to myosin.
ATP supplies the energy for muscle contraction.
Myosin filaments do all the work. The actin filaments just sit there.

37. Figure 09.04

38. Myosin filaments breakdown ATP and have crossbridges that pull the actin filaments toward the center of the sarcomere.

39. Contraction of Skeletal Muscle as a whole

40. Figure 09.06

41. Graded Responses Different degrees of shortening
Different numbers of muscles contract

42. Graded muscle contractions can be produced in two ways:
By changing the speed of muscle stimulation
By changing the number of muscle cells being stimulated

43. Providing Energy for Muscle Contraction

44. 1. Direct phosphorylation of ADP by creatine phosphate (CP)
CP gives a phosphate to ADP to make ATP
ATP is regenerated in a fraction of a second
CP supplied energy used in 20 seconds

45. 2. Aerobic Respiration – ATP is made by aerobic respiration
1 glucose – 36 ATP
Fairly slow – needs continuous supply of oxygen
Adenosine Triphosphate                                                   

46. 3. Anaerobic Respiration and Lactic Acid Formation
No oxygen
2 ATP per glucose
Lactic acid is made and builds up in muscles
5X faster than aerobic
30-40 seconds of strenuous exercise
Problems: needs lots of glucose
Small amount of ATP produced per glucose
Lactic acid

47. 3. Anaerobic Respiration and Lactic Acid Formation
No oxygen
2 ATP per glucose
Lactic acid is made and builds up in muscles
5X faster than aerobic
30-40 seconds of strenuous exercise
Problems: needs lots of glucose
Small amount of ATP produced per glucose
Lactic acid

48. Muscle Fatigue and Oxygen Debt

49. Muscle Fatigue
Occurs when muscles are exercised strenuously

50. Fatigued
When a muscle is unable to contract even though it is being stimulated

51. Oxygen Debt
The volume of oxygen needed after exercise to get rid of the lactic acid formed during exercise

52. The major factor that effects the work that a muscle can do and how long it can do work without becoming fatigued is:
How good the blood supply is

53. When muscles lack oxygen:
Lactic acid builds up
Muscles also run out of ATP
So lack of ATP and lactic acid build up cause a muscle to stop contracting

54. The Two Types of Muscle Contractions

55. Isotonic contractions
When the force of the muscle contraction is greater than the force that is resisting the contraction
Ex. Weight is lifted

56. Isometric Contractions
When the resistance to the contraction is equal to the force generated in the muscle tissue (muscle do not contract or only a little)
Pulling on a stationary bar

58. Effect of Exercise on Muscles

59. Muscle inactivity always leads to: muscle weakening and wasting away
Regular exercise increases muscle: size, strength and endurance

60. Atrophy
Diminish in size and become weaker
result of no exercise

61. Hypertrophy
Increase in size and strength
Result of exercise

62. Anabolic steroids are sometimes taken by athletes to promote muscle growth

63. Undesirable effects of anabolic steroid use:
Cardiovascular disease
Liver and kidney dysfunction
Impotency
Sterility
Increase in rash behavior “roid rage”

64. Slow Twitch Muscle Fibers - Legs
Steadier tug
More endurance
Aerobic energy production – tire when fuel is gone
Sports useful in: long distance running, biking, jogging, swimming
Color: dark
Many mitochondria, dense capillary beds which draw more blood and oxygen

65. Fast Twitch Muscle Fibers - Breasts
Anaerobic – tire quick because of lactic acid build up
Designed for strength
Explosions of energy
Sports useful in: sprinting, weight lifting
Color: white
Few mitochondria, few blood cells

66. Aerobic or Endurance Excercise
Stronger more flexible muscles with greater resistance to fatigue
Blood supply increases as cells form more mitochondria and store more oxygen

67. Body Benefits Overall body metabolism is more efficient
Improves digestion
Skeleton stronger
Heart pumps more blood with each beat
Fat deposits cleared
Lungs are more efficient at gas exchange

68. Resistance or Isometric Exercise
A few minutes every other day
Muscles increase in size because muscle cells increase in size (not increase in number of cells)
Amount of reinforcing connective tissue also increases

69. Types of Muscles Muscles cannot push. They can only pull.
So most body movements are a result of the activity of pairs or teams of muscles acting together or against each other
Muscle groups are arranged on the skeleton so that whatever one muscle can do, another group of muscles can do in reverse

70. Naming Skeletal Muscles

71. Skeletal muscles are given names based on:
Size – gluteus maximus
Shape – deltoid
Location
Direction of fibers – rectus – up and down – transverse – horizontal
Number of attachments – biceps – 2 attachments
Action

72. Figure 09.22

73. Figure 09.23

74. Figure 09.24

75. Figure 09.25a

76. Figure 09.27b

77. Figure 09.27c

78. Figure 09.27d

79. Figure 09.28

80. Figure 09.29d

81. Figure 09.31b

82. Figure 09.34

83. Figure 09.35a

84. Figure 09.37a

85. Figure 09.37b

86. Figure 09.37c

87. Figure 09.38c

88. Figure 09.39a

89. Figure 09.39a

90. Figure 09.39b

91. Figure 09.40

92. The End